The present invention relates to multiple layer flexible packaging materials and to closed and sealed packages containing food product in such flexible packaging material.
Packagers design clear windows in packaging material to enable customers to have a clear visual image of the food product contained in the package. Any accumulation of material on the inner surface of the packaging structure impedes the clarity of the image which can be viewed.
Material can accumulate on an inner surface of the package in at least two ways. First, where the water activity of the food product in the package is 1.0, namely relative humidity of 100 percent, water can condense, out of the gaseous atmosphere in the package, onto the inner surface of the packaging material. Second, materials which are part of the contained product can transfer to the packaging structure as the product comes into contact with the packaging structure. Namely, material can rub off the product, can be transferred by abrasion, or product content can, for example and without limitation, have a selective affinity for the packaging material more so than for other ingredients of the product. Whatever the mechanism of transfer, material transferred to the packaging structure at the transparent window generally works against the objective of providing a clear window through which the product can be viewed.
Where obscurement is by condensation of liquid on the packaging structure from a moisture saturated environment inside the package, namely where water activity is 1.0, it is known to provide a surfactant or other anti-fog material at the inner surface of the packaging structure. Such anti-fog structure is believed to modify the surface tension of the moisture droplets so as to attenuate the obscuring affect of such condensation on the inner surface of the packaging structure.
However, where the water activity of the product is less than 1.0, namely about 0.4 to about 0.95, moisture generally does not condense on the inner surfaces of the packaging structure because of inadequate moisture in the package to support such condensation.
Still, in packaging some products such as jerky, where the water activity is less than 0.95, after packaging the product, a material deposit develops on the inner surface of the packaging structure, which material deposit attenuates the clarity of the visual image of the contained product.
It is an object of the invention to provide, at the inner surface of the packaging structure, anti-transfer material which attenuates transfer of food product extract to the packaging structure.
It is another object to provide a closed and sealed package, having a food product contained therein, wherein an anti-transfer material at inner surfaces of the package attenuates transfer of food product extract from the food product to the packaging structure.
It is yet another object to provide a multiple layer flexible packaging structure wherein an anti-transfer material at a surface of the packaging structure is capable of attenuating transfer of food product extract from a food product to the packaging structure.
This invention comprehends a generally transparent flexible packaging structure having an anti-transfer layer which, in a closed and sealed package, is at or close to an interior surface of the package. A contained food product in the package has a tendency to deposit an e.g. fat, sugar, water or other component on the interior surface of the flexible packaging material and to thereby have a visually obscuring affect on the transparency of the packaging structure. Anti-transfer material in the anti-transfer layer migrates to the interior surface of the package and interacts with the visually-obscuring component of the contained food product, thereby to attenuate or eliminate the visually obscuring affect of such component.
In a first family of embodiments, the invention comprehends a closed and sealed package. The package comprises a flexible packaging structure comprising at least two layers and defining a closed and sealed containment structure. The flexible packaging structure comprises a substrate comprising one or more layers of polymeric material and an anti-transfer layer comprising a film-forming polymeric composition containing about 0.4 percent by weight to about 3 percent by weight of an anti-transfer material; and a contained food product in the closed and sealed package. The food product has a water activity in the closed and sealed package of about 0.4 to about 0.95 whereby relative humidity inside the package is less than 100 percent. The food product has a tendency to deposit a visually obscuring component thereof on the flexible packaging structure when in contact with the flexible packaging structure. The anti-transfer material is effective in the flexible packaging structure, upon contact of the food product with the packaging structure, to attenuate the visually obscuring affect of the visually obscuring component of the food product.
In preferred embodiments, the anti-transfer material is dispersed within the composition of the anti-transfer layer.
Further to preferred embodiments, the anti-transfer material is selected from the group consisting of primary alcohols having molecular weight greater than 200, polyethylene glycol, polypropylene glycol, glycerol, ethoxylated alcohols, glycerol monostearate, glycerol monooleate, esters of adipic acid, sorbitan monolaurate, sorbitan monooleate, ethoxylated sorbitan monolaurate, cocoamine, tallow amine, stearyl amine, ethoxylated stearyl amine, microcrystalline wax, carnauba wax, montan ester waxes, and polyethylene having molecular weight less than 4000.
In preferred embodiments, especially for interacting with fat components of the food product, the anti-transfer material comprises a short chain fatty acid or fatty acid derivative having a 12-carbon to 22-carbon chain.
In preferred embodiments, the anti-transfer material is dispersed in the anti-transfer layer, and is operative to migrate from within the anti-transfer layer to an interior surface of the packaging structure and to form an effectively protective coating on the interior surface of the packaging structure.
In highly preferred embodiments, the anti-transfer layer comprises ethylene vinyl acetate copolymer as a primary polymer.
In certain embodiments, the anti-transfer layer is comprised in a seal composite, wherein a primary polymer in the anti-transfer layer comprises ethylene vinyl acetate copolymer and wherein the seal composite further comprises a second layer comprising a second different ethylene-based polymer composition and wherein the second layer of the seal composite is tougher than the anti-transfer layer.
In preferred embodiments, the anti-transfer material is effective to attenuate the visually obscuring affect of at least one of fat, sugar, and water at water activity of about 0.4 to about 0.95.
In a second family of embodiments, the invention comprehends a multiple-layer anti-transfer film about 3.5 to about 8 mils thick. The film comprises a first substrate layer on a first surface of the film. The first substrate layer comprises an olefin-based polymer as a primary component thereof. The first substrate layer comprises about 16 weight percent to about 33 weight percent of the anti-transfer film. The anti-transfer film further comprises a polymeric seal composite comprising about 50 weight percent to about 70 weight percent of the anti-transfer film. The seal composite comprises a polymeric, olefin-based anti-transfer layer. The anti-transfer layer has about 0.4 weight percent to about 3 weight percent of an anti-transfer material generally dispersed through a thickness thereof. The anti-transfer layer is effective, upon contact with a food product in a closed and sealed package, and wherein the food product has a tendency to deposit a visually obscuring component thereof on an enclosing polymeric packaging structure, to attenuate the visually obscuring affect of the visually obscuring component.
In a third family of embodiments, the invention comprehends a method of packaging a food product. The method comprises providing, for packaging, a food product having a water activity in a closed and sealed package, of about 0.4 to about 0.95; and packaging the food product in a closed and sealed package comprising a flexible packaging structure, the flexible packaging structure comprising at least two layers and including (i) a substrate comprising one or more layers of polymeric material, and (ii) an anti-transfer layer comprising a film-forming polymeric composition containing about 0.4 percent by weight to about 3 percent by weight of an anti-transfer material dispersed within the composition of the anti-transfer layer. The food product has a tendency to deposit a visually obscuring component on the flexible packaging structure when in contact with the flexible packaging structure, and the anti-transfer material is effective in the flexible packaging structure, upon contact with the food product, to attenuate the visually obscuring affect of the visually obscuring component of the food product.